Research On Ship's Automatic Berthing Control Based On Optimal Trajectory Planning

With the rapid development of new concepts and technologies such as big data,Internet and artificial intelligence,the level of ship intelligence has been continuously improved.Since related technologies of smart ships have always been the focus of research,its automatic berthing operation is the most delicate but also one of the most important links,especially the automatic berthing of ships,which is more complicated in trajectory planning and control.As the ship becomes larger,it requires large inertia and low acceleration during the berthing process.The ship has a certain delay in the control response,and the ship's motion is strongly nonlinear,which makes the optimization of the berth trajectory produce a large-scale nonlinear optimization problem.Therefore,it is difficult to plan the ship's berthing trajectory through common robot trajectory planning algorithms.For intelligent ship berthing,trajectory planning and control must not only plan a safe and reliable berthing trajectory,but also optimize the corresponding control amount to make the ship's motion meet the dynamic requirements.In this paper,the ship dynamic model including control variables is used.Based on the initial adjustment of the control variables to generate the initial berth trajectory,the interior point penalty function method is used to optimize the ship berth trajectory and the corresponding control variables.The main research contents are listed as follows:(1)According to the actual situation such as low speed during ship.docking,the four-degree-of-freedom ship motion model established by Fossen is modified to obtain a three-degree-of-freedom ship motion model.Besides,MATLAB simulation is used to simulate the container ship SR108 by the turning test and the zigzag test to carry out simulation verification.Meanwhile,the validity of the model is verified by the test data.(2)Describe the problem of berth trajectory planning,propose the objective function with the best energy dynamic.constraints,this constraint increases with the docking time,resulting in the optimization of docking trajectory is a large-scale nonlinear optimization problem and perform localization during the solution.Finally,by analyzing the actual process of ship berthing,considering safety,ship maneuvering and other factors,the berthing control target is established,the berthing process is discretized,and the penalty function and constraint conditions for optimizing the ship trajectory are established in combination with the actual construction of a planning framework for ship berthing trajectory.(3)The factors influencing the energy consumption of ships in actual navigation are discussed,and the objective function representing energy consumption is constructed.First,assume the berthing scene,using the ship motion model containing the control amount,and taking the container ship SR108 as the simulation object,the initial berthing trajectory is obtained by continuously debugging the control amount.Then combined with the internal penalty function method optimization strategy,the non-linear optimization function Fmincon is used to optimize the ship's berthing trajectory.The normalization of the initial variables reduces the optimization complexity,shortens the optimization time,and continuously changes during the optimization process the target function corresponds to the weight of the variable,and finally obtains the variable weight that can represent the optimal energy consumption,optimizes the optimal berth trajectory,verifies the feasibility of the internal point penalty function method for optimizing the ship trajectory,and can optimize the corresponding control amount.Finally,the real berthing scene of Dalian Port is selected,and the ship's berthing process is more strictly constrained after optimization.The optimal berthing trajectory and corresponding control amount are obtained,and the dynamic effect comparison is established through the MATLAB environment.The experimental data shows that the optimization strategy is.also applicable to real docking scenarios.The results show that the strategy of ship berth trajectory optimization based on the ship dynamics model can not only plan the optimal berth trajectory,but also obtain the corresponding control amount.The optimal control amount is mainly reflected in the significantly reduced propeller control speed,which can greatly save time and energy.Therefore,it has a certain reference value and practical significance in actual use.